TLA Line data Source code
1 : //
2 : // Copyright (c) 2026 Michael Vandeberg
3 : //
4 : // Distributed under the Boost Software License, Version 1.0. (See accompanying
5 : // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
6 : //
7 : // Official repository: https://github.com/cppalliance/corosio
8 : //
9 :
10 : #ifndef BOOST_COROSIO_CONNECT_HPP
11 : #define BOOST_COROSIO_CONNECT_HPP
12 :
13 : #include <boost/corosio/detail/config.hpp>
14 :
15 : #include <boost/capy/cond.hpp>
16 : #include <boost/capy/io_result.hpp>
17 : #include <boost/capy/task.hpp>
18 :
19 : #include <concepts>
20 : #include <iterator>
21 : #include <ranges>
22 : #include <system_error>
23 : #include <utility>
24 :
25 : /*
26 : Range-based composed connect operation.
27 :
28 : These free functions try each endpoint in a range (or iterator pair)
29 : in order, returning on the first successful connect. Between attempts
30 : the socket is closed so that the next attempt can auto-open with the
31 : correct address family (e.g. going from IPv4 to IPv6 candidates).
32 :
33 : The iteration semantics follow Boost.Asio's range/iterator async_connect:
34 : on success, the successful endpoint (or its iterator) is returned; on
35 : all-fail, the last attempt's error code is returned; on an empty range
36 : (or when a connect_condition rejects every candidate),
37 : std::errc::no_such_device_or_address is returned, matching the error
38 : the resolver uses for "no results" in posix_resolver_service.
39 :
40 : The operation is a plain coroutine; cancellation is propagated to the
41 : inner per-endpoint connect via the affine awaitable protocol on io_env.
42 : */
43 :
44 : namespace boost::corosio {
45 :
46 : namespace detail {
47 :
48 : /* Always-true connect condition used by the overloads that take no
49 : user-supplied predicate. Kept at namespace-detail scope so it has a
50 : stable linkage name across translation units. */
51 : struct default_connect_condition
52 : {
53 : template<class Endpoint>
54 HIT 20 : bool operator()(std::error_code const&, Endpoint const&) const noexcept
55 : {
56 20 : return true;
57 : }
58 : };
59 :
60 : } // namespace detail
61 :
62 : /* Forward declarations so the non-condition overloads can delegate
63 : to the condition overloads via qualified lookup (qualified calls
64 : bind to the overload set visible at definition, not instantiation). */
65 :
66 : template<class Socket, std::ranges::input_range Range, class ConnectCondition>
67 : requires std::convertible_to<
68 : std::ranges::range_reference_t<Range>,
69 : typename Socket::endpoint_type> &&
70 : std::predicate<
71 : ConnectCondition&,
72 : std::error_code const&,
73 : typename Socket::endpoint_type const&>
74 : capy::task<capy::io_result<typename Socket::endpoint_type>>
75 : connect(Socket& s, Range endpoints, ConnectCondition cond);
76 :
77 : template<class Socket, std::input_iterator Iter, class ConnectCondition>
78 : requires std::convertible_to<
79 : std::iter_reference_t<Iter>,
80 : typename Socket::endpoint_type> &&
81 : std::predicate<
82 : ConnectCondition&,
83 : std::error_code const&,
84 : typename Socket::endpoint_type const&>
85 : capy::task<capy::io_result<Iter>>
86 : connect(Socket& s, Iter begin, Iter end, ConnectCondition cond);
87 :
88 : /** Asynchronously connect a socket by trying each endpoint in a range.
89 :
90 : Each candidate is tried in order. Before each attempt the socket is
91 : closed (so the next `connect` auto-opens with the candidate's
92 : address family). On first successful connect, the operation
93 : completes with the connected endpoint.
94 :
95 : @par Cancellation
96 : Supports cancellation via the affine awaitable protocol. If a
97 : per-endpoint connect completes with `capy::cond::canceled` the
98 : operation completes immediately with that error and does not try
99 : further endpoints.
100 :
101 : @param s The socket to connect. Must have a `connect(endpoint)`
102 : member returning an awaitable, plus `close()` and `is_open()`.
103 : If the socket is already open, it will be closed before the
104 : first attempt.
105 : @param endpoints A range of candidate endpoints. Taken by value
106 : so temporaries (e.g. the `std::vector<endpoint>` returned from
107 : `resolver::resolve`) remain alive for the coroutine's lifetime.
108 :
109 : @return An awaitable completing with
110 : `capy::io_result<typename Socket::endpoint_type>`:
111 : - on success: default error_code and the connected endpoint;
112 : - on failure of all attempts: the error from the last attempt
113 : and a default-constructed endpoint;
114 : - on empty range: `std::errc::no_such_device_or_address` and a
115 : default-constructed endpoint.
116 :
117 : @note The socket is closed and re-opened before each attempt, so
118 : any socket options set by the caller (e.g. `no_delay`,
119 : `reuse_address`) are lost. Apply options after this operation
120 : completes.
121 :
122 : If auto-opening the socket fails during an attempt, that attempt
123 : completes with the open error (inherits the contract of
124 : `Socket::connect`).
125 :
126 : @par Example
127 : @par !example connect
128 : */
129 : template<class Socket, std::ranges::input_range Range>
130 : requires std::convertible_to<
131 : std::ranges::range_reference_t<Range>,
132 : typename Socket::endpoint_type>
133 : capy::task<capy::io_result<typename Socket::endpoint_type>>
134 12 : connect(Socket& s, Range endpoints)
135 : {
136 : detail::default_connect_condition cond;
137 12 : return corosio::connect(s, std::move(endpoints), cond);
138 : }
139 :
140 : /** Asynchronously connect a socket by trying each endpoint in a range,
141 : filtered by a user-supplied condition.
142 :
143 : For each candidate the condition is invoked as
144 : `cond(last_ec, ep)` where `last_ec` is the error from the most
145 : recent attempt (default-constructed before the first attempt). If
146 : the condition returns `false` the candidate is skipped; otherwise a
147 : connect is attempted.
148 :
149 : @param s The socket to connect. See the non-condition overload for
150 : requirements.
151 : @param endpoints A range of candidate endpoints, taken by value.
152 : @param cond A predicate invocable with
153 : `(std::error_code const&, typename Socket::endpoint_type const&)`
154 : returning a value contextually convertible to `bool`.
155 :
156 : @return Same as the non-condition overload. If every candidate is
157 : rejected, completes with `std::errc::no_such_device_or_address`.
158 :
159 : If auto-opening the socket fails, the attempt completes with the
160 : open error.
161 : */
162 : template<class Socket, std::ranges::input_range Range, class ConnectCondition>
163 : requires std::convertible_to<
164 : std::ranges::range_reference_t<Range>,
165 : typename Socket::endpoint_type> &&
166 : std::predicate<
167 : ConnectCondition&,
168 : std::error_code const&,
169 : typename Socket::endpoint_type const&>
170 : capy::task<capy::io_result<typename Socket::endpoint_type>>
171 16 : connect(Socket& s, Range endpoints, ConnectCondition cond)
172 : {
173 : using endpoint_type = typename Socket::endpoint_type;
174 :
175 : std::error_code last_ec;
176 :
177 : for (auto&& e : endpoints)
178 : {
179 : endpoint_type ep = e;
180 :
181 : if (!cond(
182 : static_cast<std::error_code const&>(last_ec),
183 : static_cast<endpoint_type const&>(ep)))
184 : continue;
185 :
186 : if (s.is_open())
187 : s.close();
188 :
189 : auto [ec] = co_await s.connect(ep);
190 :
191 : if (!ec)
192 : co_return {std::error_code{}, std::move(ep)};
193 :
194 : if (ec == capy::cond::canceled)
195 : co_return {ec, endpoint_type{}};
196 :
197 : last_ec = ec;
198 : }
199 :
200 : if (!last_ec)
201 : last_ec = std::make_error_code(std::errc::no_such_device_or_address);
202 :
203 : co_return {last_ec, endpoint_type{}};
204 32 : }
205 :
206 : /** Asynchronously connect a socket by trying each endpoint in an
207 : iterator range.
208 :
209 : Behaves like the range overload, except the return value carries
210 : the iterator to the successfully connected endpoint on success, or
211 : `end` on failure. This mirrors Boost.Asio's iterator-based
212 : `async_connect`.
213 :
214 : @param s The socket to connect.
215 : @param begin The first candidate.
216 : @param end One past the last candidate.
217 :
218 : @return An awaitable completing with `capy::io_result<Iter>`:
219 : - on success: default error_code and the iterator of the
220 : successful endpoint;
221 : - on failure of all attempts: the error from the last attempt
222 : and `end`;
223 : - on empty range: `std::errc::no_such_device_or_address` and
224 : `end`.
225 :
226 : If auto-opening the socket fails, the attempt completes with the
227 : open error.
228 : */
229 : template<class Socket, std::input_iterator Iter>
230 : requires std::convertible_to<
231 : std::iter_reference_t<Iter>,
232 : typename Socket::endpoint_type>
233 : capy::task<capy::io_result<Iter>>
234 4 : connect(Socket& s, Iter begin, Iter end)
235 : {
236 : return corosio::connect(
237 4 : s, std::move(begin), std::move(end),
238 4 : detail::default_connect_condition{});
239 : }
240 :
241 : /** Asynchronously connect a socket by trying each endpoint in an
242 : iterator range, filtered by a user-supplied condition.
243 :
244 : @param s The socket to connect.
245 : @param begin The first candidate.
246 : @param end One past the last candidate.
247 : @param cond A predicate invocable with
248 : `(std::error_code const&, typename Socket::endpoint_type const&)`.
249 :
250 : @return Same as the plain iterator overload. If every candidate is
251 : rejected, completes with `std::errc::no_such_device_or_address`.
252 :
253 : If auto-opening the socket fails, the attempt completes with the
254 : open error.
255 : */
256 : template<class Socket, std::input_iterator Iter, class ConnectCondition>
257 : requires std::convertible_to<
258 : std::iter_reference_t<Iter>,
259 : typename Socket::endpoint_type> &&
260 : std::predicate<
261 : ConnectCondition&,
262 : std::error_code const&,
263 : typename Socket::endpoint_type const&>
264 : capy::task<capy::io_result<Iter>>
265 4 : connect(Socket& s, Iter begin, Iter end, ConnectCondition cond)
266 : {
267 : using endpoint_type = typename Socket::endpoint_type;
268 :
269 : std::error_code last_ec;
270 :
271 : for (Iter it = begin; it != end; ++it)
272 : {
273 : endpoint_type ep = *it;
274 :
275 : if (!cond(
276 : static_cast<std::error_code const&>(last_ec),
277 : static_cast<endpoint_type const&>(ep)))
278 : continue;
279 :
280 : if (s.is_open())
281 : s.close();
282 :
283 : auto [ec] = co_await s.connect(ep);
284 :
285 : if (!ec)
286 : co_return {std::error_code{}, std::move(it)};
287 :
288 : if (ec == capy::cond::canceled)
289 : co_return {ec, std::move(end)};
290 :
291 : last_ec = ec;
292 : }
293 :
294 : if (!last_ec)
295 : last_ec = std::make_error_code(std::errc::no_such_device_or_address);
296 :
297 : co_return {last_ec, std::move(end)};
298 8 : }
299 :
300 : } // namespace boost::corosio
301 :
302 : #endif
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